This proposal is based on a recently published study showing that a minor subset of dendritic cells, the CD11c+CD103+ DC, those under the control of the Batf3 transcription factor, are absolutely required for diabetes development in NOD mice. These DCs are found both in islets and pancreatic lymph nodes and act as gate-keepers for diabetes initiation. Our aims center on discovering the processes whereby CD103+DC localize in islets. We combine examination of chemokines, antibodies, and live imaging with new preliminary findings that point to NOR mice having a defect in islets CD103+ DC, but not in pLNs. These areas of emphasis may point to strategies that may be translated to human T1D. Aim 1 investigates the mechanism of CD103+ DC entry into islets. The role of chemokines in CD103+ DC recruitment will be examined both in vitro and in vivo. Chemokine blockade will be tested in vivo. In vitro migration assays will define chemokines with the potential to recruit NOD-derived CD103+ DC to islets. RT- PCR will be used to determine which chemokines exist in islets of NOD mice at different times. Aim 2 will generate and examine several reagents intended to deplete or trace CD103+ DC in the NOD mouse. We have just generated an Xcr1-/- mice using Crispr/Cas technology which should bring definitive information on the role of this chemokine receptor in the islet localization of the CD103+ DCs. We will follow the same approaches used to examine the Batf3-/- mice just published. In a second subaim, a NOD.Xcr1-mOrange reporter mouse will be generated and used to trace the movement of CD103+ DC in the pancreas using live imaging approaches. We want to examine the traffic of CD103+DC in the pancreas and determine whether it may be the cell that transmigrates to the pLN. Finally an anti-Xcl1 monoclonal antibodies will be tested for its effects on CD103+ DC migration and protection from diabetes. Aim 3 takes advantage of our recent finding that NOR mice, which share 88% of their genome with NOD, lack the intra islet CD103+ DC but have them in LNs. By comparing the Batf3-/- mice with the NORs we expect to understand the mechanisms controlling early entrance of cells into islets. We examine this strain, and substrains containing NOR-derived alleles, to address the genetic behind the CD103+ DC entry into islets.